Since the advent of letter writing, closure systems for paper products such as envelopes have progressed from sealing wax to more innovative closure systems that use a variety of adhesives and sealing mechanisms. Many of these closure systems often require wetting the adhesive or removing an additional element such as a pull tear or release paper.
The purpose for developing some of these closure systems was to improve convenience for the user when sending paper products such as envelopes, as well as trying to increase the confidentiality associated with sending letters. Prior art closure systems have been devised to address some of the aforenoted problems with closure systems.
For example, U.S. Pat. No. 5,474,229 issued to Shimazaki on Dec. 12, 1995 describes a method and apparatus for stacking pressure-sensitive adhesive envelopes. The invention relates to a stack of envelopes wherein each envelope can be easily removed from the stack and used without having to moisten the flap. Specifically the flaps of the envelopes are treated on the backside with a release coating and on the front side with a pressure sensitive adhesive. The envelopes are stacked with the flaps open so that there is an impermanent, adhering interface between the release coating and the pressure sensitive adhesive.
U.S. Pat. No. 5,642,855 issued to Michlin on Jul. 1, 1997 discloses a composite outgoing mailer and return envelope form. The invention describes a one piece Z-folding form for a outgoing mailer. With the removal of tear strips from two sides of the outgoing mailer and removable panels, the remainder may be folded into a return envelope.
U.S. Pat. No. 5,400,594 issued to Kaye on Mar. 28, 1995 discloses a reversible-returnable envelope blank. Specifically the reversible and returnable envelope blank is generally cross-shaped and uses a non-permanent reusable, resealable low tack pressure sensitive adhesive so that the envelope can be folded inside out and used as a return envelope.
U.S. Pat. No. 5,375,764 issued to Sauerwine on Dec. 27, 1994 describes a double parallel heat seal mailer. The invention discloses a double parallel mailer which may include a return envelope with a side edge opening or a booklet. More specifically the mailer includes a first outgoing portion and a return portion which can be detached from the first outgoing portion.
U.S. Pat. No. 5,052,613 issued to Lin on Oct. 1, 1991, describes a two-way envelope. More specifically the invention discloses an envelope that may be used for both an original and return mailers and includes removable and reusable address labels. The invention further describes a number of different ways to fold the mailer so that there is an outgoing portion and a second return portion.
A closure system for both paper and plastic products that does not require any moistening of the adhesive, allows for easy application to envelopes or mailing systems, and allows for easy storage, printing and use of the paper and plastic products is desirable.